There are three phases in the development of new drugs aimed at determining adverse reactions or side effects. Each of these phases produces many different pieces of information. All of this leads to a major problem involving the professional/industrial and/or academic libraries serving the scientific-medical community through their information centers. The major components of this problem are definition of adverse reactions, their collection, classification, storage and retrieval. The objective of this report is to lend insight into this complex area and to direct suggestions to the information scientists who may assist the clinicians involved in medication selection. (Author/SJ)